An impact wrench has a clutch which re-engages periodically to deliver a series of repeated hammer blows to an anvil. The anvil may be formed integrally with a drive shank having a portion extending from the tool. The extending portion of the drive shank carries a driven impact socket which engages a nut or bolt head. In order to accommodate the relatively-heavy impact loads, the socket has a square (or other polygonal) cross-sectioned recess to receive the corresponding square cross-sectioned configuration of the drive shank. Moreover, in order to preclude axial displacement of the socket relative to the drive shank, the socket is further keyed to the shank by a transverse locking pin. This pin is received mutually within a transverse bore in the drive shank and a pair of alined radial bores in the socket. Upon removal of the pin, the socket may be removed from the shank.
In the prior art, of which I am aware, various means have been provided for retaining the pin in its normal keying position. For example, in U.S. Pat. No. 2,326,317, the radial bores in the socket are covered by a retainer ring formed from an elastic material. This retainer ring may comprise a rubber band which surrounds the locking pin and frictionally engages the cylindrical surface of the socket member. This rubber band may be removed or shifted manually to uncover the radial bores in the socket and allow the locking pin to be removed. If the rubber band breaks during operation of the tool, the centrifugal forces which are generated by the tool (which is a high-speed power-operated impact wrench) may cause the locking pin to become dislodged, thereby resulting in a safety hazard. Moreover, the rubber band is not convenient to use and may become separated from the tool and misplaced inadvertently.
The prior art has also resorted to various spring-loaded retaining clips for coupling pins. For example, in U.S. Pat. No. 2,739,000, a spring clip has dimpled ends for receiving the respective ends of a coupling pin. This spring-clip retainer must be removed entirely to expose the coupling pin. Furthermore, in U.S. Pat. No. 2,291,253, a collar may be moved axially to expose a locking or coupling pin and facilitate the removal thereof. The collar has an inturned flange surrounding a shaft, and the collar is biased by a coil spring piloted on the shaft and bearing against the flange. While apparently functional for the purposes intended, these prior arrangements are cumbersome and costly and are not readily adaptable to a retainer for the drive socket of a portable power-operated impact wrench.